When Henning Wackerhage lines up for today's London Marathon, he will have one key advantage over the rest of the race's 48,000 competitors. The geneticist knows exactly what it would take for a runner to become fit enough to complete the 26 mile and 385 yard course in an hour and a half, which is 30 minutes quicker than the world record.

Such knowledge suggests we may get a sensational performance from the Aberdeen University researcher. Wackerhage is quick to dismiss such expectations, however.

'To run a one-and-a-half-hour marathon requires not just a rigorous training programme,' he said. 'It also requires the runner to have a very special set of genes. To date, no one on this planet has been found with such a set.'

Wackerhage yesterday outlined some of the most important of these marathon genes in a lecture, 'Tips for Dr Frankenstein: How to Bio-Engineer a sub-1hr 30 min Marathon Runner', at the Royal Society of Medicine's Marathon Medicine conference in London before heading for the marathon's start at Greenwich. As he pointed out, a gene usually comes in more than one variety and these variations can have a crucial impact on the body.

A classic example is provided by Eero Mantyranta, the Finnish cross-country skier who won two golds in the 1964 Winter Olympics - a performance that was eventually traced by doctors to his possession of a rare mutation in his EPO-receptor genes that caused him to churn out unusually high levels of red blood cells (which carry oxygen to our muscles and give them power). 'Cross-country skiing and long-distance running require the same types of physique,' said Wackerhage. 'So any with his EPO-receptor gene mutation would have a great advantage at marathon.'

Other attributes that would aid marathon runners include elevated levels of glycogen, which stores energy; high muscle mass; and strong hearts and lungs. Again Wackerhage has studied the inherited roots of these and found the genes that play a key role in their development, though most involve research on mice not humans. 'Mouse genes are very similar to human genes, however,' he said. 'They reflect what is going on in a runner.'

One key factor found by researchers is the gene that controls the production of the PEPCK enzyme. It comes in several variants, one of which produces startling results when mice are genetically engineered with it. They turn into extreme athletes, whizzing round the wheels in their cages for hours. Hence PEPCK's nickname: the Speedy Gonzales gene.

'Just having the right EPOR and PEPCK variants in a runner would make him or her almost unbeatable,' said Wackerhage. In fact, there is a minimum of 23 other variants in genes that would lead to dramatic improvements in performances, he said. 'It is very unlikely any person possesses all of these or even most of them, however.'

To create a super-runner would therefore require bio-engineering. However such a prospect is dismissed by Wackerhage. 'Attempting this in practice is likely to be either ineffective, because introducing genetic material into muscles is difficult; or it will trigger serious complications that could result in death; or it will be detected by gene tests, leading to disqualification.' In other words, we will have to wait for a while for the emergence of the super-athlete.

Certainly Wackerhage has no expectations today: 'I will be lucky if I run it in under three hours, 15 minutes.'